The "L Number" system began when two German magazines began featuring newly discovered Loricariids in their magazines. Since these species were not yet described to science, the magazines began assigning them "L numbers". The German magazine "DATZ" (Die Aquarien und Terrarienzeitschrift) started with the designation L1 for the Loricariid which has now been described as Pterygoplichthys joselimaianus. So now L1 is retired. Another German magazine "Das Aquarium", also began to run a similar feature in its magazine and labeled the fishes as LDA followed by a number. At the time of writing, the DATZ L system is somewhere above L370 and the LDA system is above LDA 70 - neither show signs of slowing. This numbering system has caught on and new species of Corydoras are now being assigned "C Numbers".

Finally, along came the Aqualog series of books and they published a book with all the known L numbers with photos or drawings of each fish. This makes things a lot easier since not all of us, in America or the UK, have access to back issues of German aquarium magazines. There are apparently some problems though because not all of the photos in the Aqualog book match the species in the photos that ran in the original magazines. So sometimes it is necessary to note where you L number is coming from (magazine or book).